How Does Diamond Grading Work?
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The four C's
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Diamonds are precious gemstones known for their normally clear color and exceptional hardness. Since diamonds are one of the most sought-after gemstones, each one is carefully observed and given a grade based on four criteria that determine their overall value. These criteria are carat weight, clarity, color and cut.
Carat Weight
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The carat is a unit of weight measurement used to weigh diamonds and other precious stones. One of the most important factors in calculating the value of a diamond is the size of the gem, which is determined by its carat weight. Since larger diamonds are exponentially rarer than smaller diamonds, the price per carat of a larger diamond will be more than a smaller diamond. For example, a 2-carat diamond will generally be worth more than two 1-carat diamonds, with all else held equal. One carat is equal to 200mg.
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Clarity
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The clarity of a diamond refers to the size and number of blemishes (external imperfections) and inclusions (internal imperfections) within the stone. The scale of clarity ranges from I3, which means very included, to F, which means flawless. The value of a diamond will vary significantly depending in its clarity rating: a 1-carat diamond rated F or IF (internally flawless) can cost well over twice as much as a similarly-sized diamond of lesser clarity. The clarity grading scale is based on how visible imperfections are at various degrees of magnification. An I-rated diamond will have imperfections visible to the naked eye, while diamonds with better clarity will require greater and greater magnification for the imperfections to be seen.
Color
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The color of a diamond is graded on a scale from D to Z, D being the clearest, or colorless, and Z being the most yellowish. In the color-grading system, D to F are considered colorless, G to J are considered near colorless and anything lower than J is considered slightly to heavily tinted. (Diamonds of deep color are called "fancy.") As with the other grades of diamonds, a very clear color rating makes a diamond more valuable. However, each step up the color grading scale usually does not increase the cost of a diamond as much as a step up the clarity grading scale. Diamonds with a color rating of D are much more common than diamonds with a clarity rating of F.
Cut
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The final grade of a diamond is its cut, which attempts to gauge weather a diamond was shaped in a way that gives it maximum light reflection and sparkle. Since a raw diamond is usually spherical and a cut diamond is not, a significant amount of carat weight must be shaved off to cut a rough diamond into a stone suitable for jewelery. A cut that attempts to maintain more carat weight may sacrifice the perfect balance of angles to make the facets reflect light. Cut is graded from 1 to 8, with 1 being the best, or excellently cut, and 8 being the worst.
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